Sleep apnea, norepinephrine-release rate, and daytime hypertension

Correlation of mean platelet volume and red blood cell distribution width with obstructive sleep apnoea syndrome severity

INTRODUCTION

Mean platelet volume (MPV) and red blood cll distribution width (RDW) have been assosiated with sleep apnea syndrome severity.

OBJECTIVE

To investigate the correlation of mean platelet volume and red blood cell distribution width with obesity sleep apnoea syndrome (OSAS) severity.

METHODS

Ninety patients underwent PSG. Patients with an apnoea-hypopnoea index (AHI) <5 were used as controls. Patients with AHI >5 were divided into mild: 5 ≤ AHI <15, moderate: 15≤ AHI <30 and severe OSAS: AHI ≥30. Patients >65 years, with body mass index (BMI) >40, central sleep apnoea syndrome, cardiovascular or other significant comorbidities were excluded. Blood sample collection occurred one day before polysomnography (PSG).

RESULTS

Sixty-four patients were included in our study. Fifty-seven (89.1%) had OSAS (16% mild, 25% moderate and 48.4% severe) while the remaining 7 (10.1%) were used as controls. MPV was similar among groups [8.1 (7.1, 9.2) vs 7.9 (6.8, 10.1) vs 8.5 (7.4, 9.1) vs 8.4 (7.6, 9.7), P = .930 for control, mild, moderate and severe OSAS, respectively]. RDW did not differ between OSAS patients and control [median (IQR) 14.4 (13.4, 15.3) vs 14.0 (13.5, 16.7), P = .950], while there was no significant difference among different stages of OSAS severity [14.0 (13.5, 16.7) vs 13.9 (11.4, 14.8) vs 14.4 (14.0, 15.3) vs 14.4 (13.3, 15.6), P = .517] for control, mild, moderate and severe OSAS, respectively.

CONCLUSION

OSAS patients have elevated levels of RDW and MPV compared to controls; however, there was no association between OSAS severity and MPV or RDW.

Possible Molecular Mechanisms of Hypertension Induced by Sleep Apnea Syndrome/Intermittent Hypoxia

Intermittent hypoxia (IH) is a central characteristic of sleep apnea syndrome (SAS), and it subjects cells in the body to repetitive apnea, chronic hypoxia, oxygen desaturation, and hypercapnia. Since SAS is linked to various serious cardiovascular complications, especially hypertension, many studies have been conducted to elucidate the mechanism of hypertension induced by SAS/IH. Hypertension in SAS is associated with numerous cardiovascular disorders. As hypertension is the most common complication of SAS, cell and animal models to study SAS/IH have developed and provided lots of hints for elucidating the molecular mechanisms of hypertension induced by IH. However, the detailed mechanisms are obscure and under investigation. This review outlines the molecular mechanisms of hypertension in IH, which include the regulation systems of reactive oxygen species (ROS) that activate the renin-angiotensin system (RAS) and catecholamine biosynthesis in the sympathetic nervous system, resulting in hypertension. And hypoxia-inducible factors (HIFs), Endotheline 1 (ET-1), and inflammatory factors are also mentioned. In addition, we will discuss the influences of SAS/IH in cardiovascular dysfunction and the relationship of microRNA (miRNA)s to regulate the key molecules in each mechanism, which has become more apparent in recent years. These findings provide insight into the pathogenesis of SAS and help in the development of future treatments.

Pathophysiological mechanisms and therapeutic approaches in obstructive sleep apnea syndrome

Obstructive sleep apnea syndrome (OSAS) is a common breathing disorder in sleep in which the airways narrow or collapse during sleep, causing obstructive sleep apnea. The prevalence of OSAS continues to rise worldwide, particularly in middle-aged and elderly individuals. The mechanism of upper airway collapse is incompletely understood but is associated with several factors, including obesity, craniofacial changes, altered muscle function in the upper airway, pharyngeal neuropathy, and fluid shifts to the neck. The main characteristics of OSAS are recurrent pauses in respiration, which lead to intermittent hypoxia (IH) and hypercapnia, accompanied by blood oxygen desaturation and arousal during sleep, which sharply increases the risk of several diseases. This paper first briefly describes the epidemiology, incidence, and pathophysiological mechanisms of OSAS. Next, the alterations in relevant signaling pathways induced by IH are systematically reviewed and discussed. For example, IH can induce gut microbiota (GM) dysbiosis, impair the intestinal barrier, and alter intestinal metabolites. These mechanisms ultimately lead to secondary oxidative stress, systemic inflammation, and sympathetic activation. We then summarize the effects of IH on disease pathogenesis, including cardiocerebrovascular disorders, neurological disorders, metabolic diseases, cancer, reproductive disorders, and COVID-19. Finally, different therapeutic strategies for OSAS caused by different causes are proposed. Multidisciplinary approaches and shared decision-making are necessary for the successful treatment of OSAS in the future, but more randomized controlled trials are needed for further evaluation to define what treatments are best for specific OSAS patients.

The Impact of Intermittent Hypoxia on Metabolism and Cognition

Intermittent hypoxia (IH), one of the primary pathologies of sleep apnea syndrome (SAS), exposes cells throughout the body to repeated cycles of hypoxia/normoxia that result in oxidative stress and systemic inflammation. Since SAS is epidemiologically strongly correlated with type 2 diabetes/insulin resistance, obesity, hypertension, and dyslipidemia included in metabolic syndrome, the effects of IH on gene expression in the corresponding cells of each organ have been studied intensively to clarify the molecular mechanism of the association between SAS and metabolic syndrome. Dementia has recently been recognized as a serious health problem due to its increasing incidence, and a large body of evidence has shown its strong correlation with SAS and metabolic disorders. In this narrative review, we first outline the effects of IH on the expression of genes related to metabolism in neuronal cells, pancreatic β cells, hepatocytes, adipocytes, myocytes, and renal cells (mainly based on the results of our experiments). Next, we discuss the literature regarding the mechanisms by which metabolic disorders and IH develop dementia to understand how IH directly and indirectly leads to the development of dementia.

Prevalence of mental illness in patients with obstructive sleep apnea – A cross-sectional study from Kashmir, India

Aim

The study aimed to evaluate the prevalence of mental illness in obstructive sleep apnea (OSA) and to examine whether patients with obstructive sleep apnea require screening for mental illness.

Methods

We performed polysomnography studies of patients that were referred from various subspecialty clinics in Kashmir from Jan 2020–December 2020. using the Mini-International Neuropsychiatric Interview (MINI plus) scale to make a psychiatric diagnosis. We administered the General Health Questionnaire – 28 (GHQ – 28), Hamilton Depression Rating Scale (HAM-D), and Hamilton Anxiety Rating Scale (HAM-A) to patients. Descriptive statistics and correlations were used for data analysis.

Results

182 patients underwent polysomnography, 85 (46.7%) of which were suffering from mental illness Based on the Apnea-Hypopnea Index score, 8 (4.39%) patients had mild, 35 (41.1%) had moderate and 42 (49.4%) had severe OSA. The mean GHQ -28 score was significantly higher in patients with Obstructive sleep apnea (p < 0.001) (11.34 ± 8.2) as compared to non-Obstructive sleep apnea patients (1.98 ± 4.38).

Conclusions

This study demonstrates the increased prevalence of anxiety and depression in patients with OSA. Therefore, we recommend timely screening for any mental health issues in patients with OSA and necessary interventions to address the issues, thus preventing mental health morbidities in patients with OSA this would help subsequently in an improved lifestyle.

•

This study highlighted the prevalence of mental illness in obstructive sleep apnea (OSA).

•

Almost one-half of the patients diagnosed with OSA had mental illness.

•

Appropriate measures should be undertaken to control prevalence of anxiety and depression in patients with OSA.

An Improved Model of Moderate Sleep Apnoea for Investigating Its Effect as a Comorbidity on Neurodegenerative Disease

Sleep apnoea is a highly prevalent disease that often goes undetected and is associated with poor clinical prognosis, especially as it exacerbates many different disease states. However, most animal models of sleep apnoea (e.g., intermittent hypoxia) have recently been dispelled as physiologically unrealistic and are often unduly severe. Owing to a lack of appropriate models, little is known about the causative link between sleep apnoea and its comorbidities. To overcome these problems, we have created a more realistic animal model of moderate sleep apnoea by reducing the excitability of the respiratory network. This has been achieved through controlled genetically mediated lesions of the preBötzinger complex (preBötC), the inspiratory oscillator. This novel model shows increases in sleep disordered breathing with alterations in breathing during wakefulness (decreased frequency and increased tidal volume) as observed clinically. The increase in dyspnoeic episodes leads to reduction in REM sleep, with all lost active sleep being spent in the awake state. The increase in hypoxic and hypercapnic insults induces both systemic and neural inflammation. Alterations in neurophysiology, an inhibition of hippocampal long-term potentiation (LTP), is reflected in deficits in both long- and short-term spatial memory. This improved model of moderate sleep apnoea may be the key to understanding why this disorder has such far-reaching and often fatal effects on end-organ function.

Intermittent Hypoxia Increased the Expression of DBH and PNMT in Neuroblastoma Cells via MicroRNA-375-Mediated Mechanism

Sleep apnea syndrome (SAS), characterized by recurrent episodes of oxygen desaturation and reoxygenation (intermittent hypoxia (IH)), is a risk factor for hypertension and insulin resistance. We report a correlation between IH and insulin resistance/diabetes. However, the reason why hypertension is induced by IH is elusive. Here, we investigated the effect of IH on the expression of catecholamine-metabolizing enzymes using an in vitro IH system. Human and mouse neuroblastoma cells (NB-1 and Neuro-2a) were exposed to IH or normoxia for 24 h. Real-time RT-PCR revealed that IH significantly increased the mRNA levels of dopamine β-hydroxylase (DBH) and phenylethanolamine N-methyltransferase (PNMT) in both NB-1 and Neuro-2a. Western blot showed that the expression of DBH and PNMT in the NB-1 cells was significantly increased by IH. Reporter assays revealed that promoter activities of DBH and PNMT were not increased by IH. The miR-375 level of IH-treated cells was significantly decreased relative to that of normoxia-treated cells. The IH-induced up-regulation of DBH and PNMT was abolished by the introduction of the miR-375 mimic, but not by the control RNA. These results indicate that IH stress increases levels of DBH and PNMT via the inhibition of miR-375-mediated mRNA degradation, potentially playing a role in the emergence of hypertension in SAS patients.

Neuroadrenergic activation in obstructive sleep apnoea syndrome: a new selected meta-analysis - revisited

BACKGROUND

Neuroadrenegic overdrive occurs in obstructive sleep apnoea syndrome (OSAS). However, the small sample size of the microneurographic studies, heterogeneity of the patients examined, presence of comorbidities, represented major weaknesses not allowing to precisely define the main features of the phenomenon, particularly in nonobese patients.

OBJECTIVE

This meta-analysis detected 14 microneurographic studies based on muscle sympathetic nerve activity (MSNA) quantification in uncomplicated OSAS of different clinical severity.

METHODS

The evaluation was extended to the relationships of MSNA with heart rate, anthropometric and blood pressure values, metabolic variables, apnoea-hypopnea index and oxygen saturation.

RESULTS

MSNA is activated markedly and almost homogeneously between studies, showing a progressive increase from the healthy state to mild, moderate and severe OSAS (46.03, 48.32, 71.84, 69.27 bursts/100 heart beats). Of special interest are the findings that MSNA is significantly related to the apnoea-hypopnea index, a marker of OSAS severity (r = 0.55, P  = 0.04) but not to BMI, as it occurs in OSAS associated with obesity, and heart rate is significantly and directly related to MSNA and apnoea-hypopnea index (r = 0.68 and r = 0.60, respectively P = 0.03 and P = 0.02), thus representing a surrogate marker of the sympathetic overdrive.

CONCLUSION

OSAS, even when uncomplicated by other cardiometabolic disease, displays a marked sympathetic activation, reflected by the MSNA and heart rate behaviour, becoming a target of therapeutic interventions aimed at exerting sympathomoderating effects, such as continuous positive airway pressure.

Erectile Dysfunction and Obstructive Sleep Apnea: A Review

Erectile dysfunction (ED) is a disease with a wide scope of etiologies. Obstructive sleep apnea (OSA) is considered one of the risk factors for ED and is less studied. A growing lot of evidence show an association between OSA and ED. This study provides an updated review of the relationship between ED and OSA and the possible physiological mechanisms of ED in patients with OSA based on the current evidence. In clinical interviews, patients with ED may benefit from a sleep evaluation. However, further clinical investigations and more basic research are needed to illustrate the relationship between ED and OSA.

Neuroadrenergic activation in obstructive sleep apnea syndrome: a systematic review and meta-analysis

BACKGROUND

Neuroadrenergic overdrive occurs in obstructive sleep apnea syndrome (OSAS). However, the small sample size of the microneurographic studies, heterogeneity of the patients examined, presence of comorbidities, represented major weaknesses not allowing to precisely define the main features of the phenomenon, particularly in nonobese patients.

OBJECTIVE

This meta-analysis evaluated 850 participants recruited in 26 microneurographic studies, based on muscle sympathetic nerve activity (MSNA) quantification in uncomplicated OSAS of different clinical severity.

METHODS

The evaluation was extended to the relationships of MSNA with heart rate (HR), anthropometric and blood pressure (BP) values, metabolic variables, apnea-hypopnea index (AHI) and oxygen saturation.

RESULTS

MSNA is activated markedly and almost homogeneously between studies, showing a progressive increase from the healthy state to mild, moderate and severe OSAS (41.6, 48.3, 65.5 and 70.7 bursts/100 heart beats, respectively, P < 0.01). Of special interest are the findings that first, MSNA is significantly related to the AHI, a marker of OSAS severity (r = 0.55, P < 0.02) and O2 saturation but not to body weight and BMI, as it occurs in OSAS associated with obesity; and second, HR is significantly and directly related to MSNA and AHI (r = 0.56 and 0.46, P < 0.03 for both), thus representing a surrogate marker of the sympathetic overdrive.

CONCLUSION

OSAS, even when uncomplicated by other cardiometabolic disease, displays a marked sympathetic activation, reflected by the MSNA and HR behavior, becoming a target of therapeutic interventions aimed at exerting sympathomoderating effects, such as continuous positive airway pressure.

Respiratory Muscle Strength as an Indicator of the Severity of the Apnea-Hypopnea Index: Stepping Towards the Distinction Between Sleep Apnea and Breath Holding

Background and objective The aim of this study was to investigate whether the maximum inspiratory and expiratory pressure are correlated with the apnea-hypopnea index (AHI) in patients with obstructive sleep apnea syndrome (OSAS). Methods Fifty-two patients with OSAS were divided into two groups (AHI, events/hours: <30, n=28, versus ≥30, n=24). For each patient, anthropometric characteristics, spirometry parameters, maximum inspiratory (MIP) and expiratory pressure (MEP), and cardiopulmonary function (CPF) parameters (oxygen uptake at rest (VO₂), carbon dioxide output (VCO₂), heart rate (HR), minute ventilation (V_E), tidal volume at inspiratory (TVin) and expiratory (TVex), breath frequency (f _β), end-tidal carbon dioxide pressure (P_ETCO₂), end-tidal oxygen pressure (P_ETO₂), and mean arterial pressure (MAP)) in sitting position for three minutes were recorded. The independent t-test was used to measure the differences between groups (events/hours <30 versus ≥30) and Pearson correlation analysis was used for statistical comparison between parameters. Results Results showed differences between groups (AHI, events/h ≥30 versus <30) in MIP (102.0±18.3 versus 91.1±12.1 % of predicted, p=0.013) and CPF parameters TVin (0.8±0.2 versus 0.7±0.1, L, p=0.047), P_ETCO₂ (34.6±4.2 versus 31.4±3.7, mmHg, p=0.007), and MAP (88.4±6.5 versus 82.9±6.2, mmHg, p=0.003). Pearson correlation analysis between respiratory muscle strength (MIP and MEP) and polysomnography (PSG) parameters, MIP is related to AHI (r=.332, p=0.016) and desaturation index (r=.439, p=0.001), as well as MEP to percent of REM sleep stage (r=-.564, p<0.001). Conclusion The data from the present study support that maximal inspiratory pressure relates to the severity of AHI and intermittent breath-holding during sleep increases the inspiratory muscle strength.

The Diagnostic-Measurement Method-Resting Energy Expenditure Assessment of Polish Children Practicing Football

Establishing the amount of energy needed to cover the energy demand of children doing sport training and thus ensuring they achieve an even energy balance requires the resting energy expenditure (REE) to be estimated. One of the methods that measures REE is the indirect calorimetry method, which may be influenced by many factors, including body composition, gender, age, height or blood pressure. The aim of the study was to assess the correlation between the resting energy expenditure of children regularly playing football and selected factors that influence the REE in this group. The study was conducted among 219 children aged 9 to 17 using a calorimeter, a device used to assess body composition by the electrical bioimpedance method by means of segment analyzer and a blood pressure monitor. The results of REE obtained by indirect calorimetry were compared with the results calculated using the ready-to-use formula, the Harris Benedict formula. The results showed a significant correlation of girls’ resting energy expenditure with muscle mass and body height, while boys’ resting energy expenditure was correlated with muscle mass and body water content. The value of the REE was significantly higher (p ≤ 0.001) than the value of the basal metabolic rate calculated by means of Harris Benedict formula. The obtained results can be a worthwhile suggestion for specialists dealing with energy demand planning in children, especially among those who are physically active to achieve optimal sporting successes ensuring proper functioning of their body.

Obstructive sleep apnoea and cardiovascular disease: a literature review

As obesity becomes more common worldwide, the prevalence of obstructive sleep apnoea (OSA) continues to rise. Obstructive sleep apnoea is a well-known disorder that causes chronic intermittent hypoxia (CIH), which is considered a risk factor for atherosclerosis directly and indirectly. Ischaemic heart disease remains the leading cause of death. Most risk factors for atherosclerosis are well understood. However, other factors such as CIH are less well understood. Several studies have investigated the pathophysiology of CIH, attempting to uncover its link to atherosclerosis and to determine whether OSA treatment can be a therapeutic modality to modify the risk for atherosclerosis. In this article, we will review the pathophysiology of OSA as an independent risk factor for cardiovascular disease and discuss the most common markers that have been studied. We will also examine the potential impact of OSA management as a risk factor modifier on the reversibility of atherosclerosis.

Effects of obstructive sleep apnea and its treatment over the erectile function: a systematic review

Erectile dysfunction (ED) is considered a condition with a broad range of etiologies. Obstructive sleep apnea (OSA) syndrome is one of the lesser studied risk factors for ED. We intend to summarize the current evidence on the relationship between OSA and sexual impairment, focusing on the results in terms of erectile function of the different therapies offered to OSA patients. A systematic review was conducted, selecting articles related to the physiology of OSA and ED, and to the treatments of OSA syndrome and their reported outcomes in erectile and sexual function. Higher prevalences of ED in the OSA groups have been published. However, whether this effect on the erectile function occurs in the entire range of OSA severities remains unclear. Several hypotheses were proposed to explain the physiology of this association. Continuous Positive Airway Pressure as a treatment for OSA patients with ED has achieved a significative improvement in the sexual parameters in most of the studies. Phosphodiesterase type 5 inhibitors (iPDE5) on demand are useful as a treatment for ED in this subgroup of patients, with high satisfaction rates. The surgical treatment for the OSA evidenced benefits over the erectile function, and the effect on the sexual satisfaction of the therapy using Mandibular Advancement Devices is still undefined.

Independent association of resting energy expenditure with blood pressure: confirmation in populations of the African diaspora

BACKGROUND

Obesity is a major risk factor for hypertension, however, the physiologic mechanisms linking increased adiposity to elevations in blood pressure are not well described. An increase in resting energy expenditure (REE) is an obligatory consequence of obesity. Previous survey research has demonstrated that REE is an independent predictor of blood pressure, and eliminates the co-linear association of body mass index. This observation has received little attention and there have been no attempts to provide a causal explanation.

METHODS

At baseline in an international comparative study on obesity, 289 participants aged 25-44 were recruited from communities in the US, the Seychelles, Ghana and South Africa and had REE measured with indirect calorimetry. All participants were thought to be free of major illness.

RESULTS

In multivariate regression models, both systolic and diastolic blood pressure were positively associated with REE (p < 0.01), while body mass index and fat mass were negatively correlated with systolic blood pressure (p < 0.01, and p < 0.05 respectively), but not diastolic blood pressure.

CONCLUSIONS

These data confirm previous reports and suggest that a common physiologic abnormality links REE and blood pressure. Elevated catecholamines, a putative metabolic characteristic of obesity, is a possible candidate to explain this association. The direct role of excess adipose tissue is open to question.

Impact of inflammation and oxidative stress on carotid intima-media thickness in obstructive sleep apnea patients without metabolic syndrome

Obstructive sleep apnea (OSA) increases the risk of cardiovascular diseases, and carotid intima-media thickness (IMT) is a good indicator of the severity of atherosclerotic disease. This study tested the hypothesis that inflammation and oxidative stress determined carotid IMT in patients with OSA. The carotid IMT, mean systolic and diastolic pressure (night and morning) were significantly higher and the level of thiols and high-density lipoprotein were significantly lower in our 121 OSA patients than in 27 controls (P < 0.05). The apnea/hypopnea index was correlated positively with E-selectin (r = 0.222, P = 0.014), total cholesterol (r = 0.185, P = 0.042), low-density lipoprotein (r = 0.264, P = 0.003) and HbA1c levels (r = 0.304, P = 0.001), but inversely with high-density lipoprotein level (r = -0.203, P = 0.025) in the 121 patients with OSA. In OSA subjects, multiple linear regression analysis revealed that age, systolic blood pressure and intercellular cell adhesion molecule-1 level associated independently with carotid IMT. Besides both age and systolic blood pressure, our study demonstrated that intercellular cell adhesion molecule-1 level was associated significantly with carotid IMT in those patients who had OSA but without metabolic syndrome.

Definition and Importance of Autonomic Arousal in Patients with Sleep Disordered Breathing

Autonomic arousal at the end of sleep apnea events are not well-explored. We prospectively studied 20 patients with obstructive sleep apnea (OSA) and 24 healthy volunteers for 2 nights with cardiorespiratory polysomnography and continuous noninvasive blood pressure (Portapres). Recordings were scored visually for cortical and autonomic arousal. In the OSA group, 2151 cortical arousals and in the controls 1089 cortical arousals were scored. Respiratory arousal caused most frequently an increase of highest mean arterial blood pressure in patients and controls. A useful definition for autonomic arousal for OSA and controls based on blood pressure and heart rate analysis was developed.

Mean Platelet Volume Decreases in Adult Patients With Obstructive Sleep Apnea After Uvulopalatal Flap Surgery

AIM

The main purpose of the study was to investigate changes in mean platelet volume (MPV) values in patients with obstructive sleep apnea syndrome (OSAS) who had undergone uvulopalatal flap (UPF) surgery.

METHOD

The study included a review of the medical records of 37 adult patients who had undergone UPF surgery after being diagnosed with OSAS. The baseline blood parameters of patients, including the MPV and platelet distribution width (PDW) values, were measured and repeated 3 months after treatment. Polysomnographic evaluations of the patients were also performed during admission and the 3rd month control. Comparisons of MPV values and their correlation with polysomnographic parameters were the main outcomes measured.

RESULTS

The blood parameters of all patients were similar except for MPV values, which were significantly lower after treatment (P < 0.001). Patients' apnea hypopnea index (AHI) and apnea episodes were significantly reduced after the UPF surgery, whereas their oxygen saturation significantly increased (P < 0.001). The MPV values were not correlated with polysomnographic parameters (P > 0.05).

CONCLUSION

The UPF surgery, which is a relatively simple surgical intervention to treat OSAS, alleviates nocturnal hypoxic episodes and lowers platelet volume. These may both be important predictors of adverse cardiovascular outcomes related to OSAS.

The sympathetic nervous system and catecholamines metabolism in obstructive sleep apnoea

Obstructive sleep apnoea (OSA) is the most common sleep disorder of breathing in middle-aged and overweight subjects. It features recurrent episodes of upper airway total (apnoea) o partial (hypopnea) collapse during sleep, which are associated with a reduction in blood oxygen saturation and with arousal from sleep to re-establish airway patency. An association of OSA with dysregulation of the autonomous nervous system (ANS) and altered catecholamines (CAs) metabolism has been contended for years. However, the pathophysiology mechanisms underlying these alterations remain to be fully clarified. Nonetheless, these alterations are deemed to play a key pathogenic role in the established association of OSA with several conditions besides arterial hypertension (HT), including coronary artery disease, stroke, and, more in general, with increased risk of cardiovascular (CV) events. Hence, in this review we will analyse the relationship between the sleep disturbances associated with OSA and the altered function of the ANS, including CAs metabolism.

Blood parameters as indicators of upper airway obstruction in children with adenoid or adenotonsillar hypertrophy

Adenotonsillar hypertrophy (ATH) is the most common cause of obstructive sleep apnea in children. This study aimed to evaluate the blood parameters of children with ATH who underwent surgery.

METHODS

The study included a review of the medical records of 130 children who underwent adenoidectomy or adenotonsillectomy with a diagnosis of adenoid hypertrophy and/or chronic tonsillitis. Patients were classified into 3 groups: group 1 (n=69) underwent adenoidectomy, group 2 (n=61) underwent adenotonsillectomy, and group 3 consisted of 82 healthy children. White blood cell count, platelet count, hemoglobin levels, mean platelet volume, and platelet distribution width values were the primary outcome measures.

RESULTS

Mean platelet volume, platelet distribution width and hemoglobin values decreased in the groups that underwent surgery. Whereas the decrease in group 1 was insignificant, it was significant in group 2. White blood cell count values increased in both group 1 (adenoidectomy) and group 2 (adenotonsillectomy), but the increase in group 2 was significant. No significant difference in platelet count was detected before versus after the operation.

CONCLUSIONS

Upper airway obstruction caused by ATH remarkably changes the blood parameters related to chronic hypoxia. Significant improvement can be achieved after adenotonsillectomy rather than adenoidectomy alone.

Hematological Parameters as Predictors of Cardiovascular Disease in Obstructive Sleep Apnea Syndrome Patients

We investigated the role of the red cell distribution width (RDW) and other parameters including platelet (PLT) count, mean platelet volume (MPV), and platelet distribution width (PDW) in patients with obstructive sleep apnea syndrome (OSAS) having cardiovascular diseases (CVDs). Patients (n = 142) having sleep disorders and who applied for a night polysomnography were included in this study. For statistical analysis, chi-square test, bivarite correlation, and logistic and stepwise regression tests were used. A positive correlation between RDW MPV, RDW, and body mass index as well as PLT and apnea-hypopnea index were observed. A negative correlation between AHI and PDW (P= .041) and a positive correlation between AHI and PLT (P= .010) were found in the patients ≥40 years old with CVD. The RDW was higher in patients ≥40 years old who had CVD (P= .016), and 19% of them had RDW >14%. The PDW (odds ratio = 6.02 [95% confidence interval = 1.3-28.2],P= .023) appeared to be associated with increased risk of hyperlipidemia in patients with severe OSAS. If these results are confirmed, RDW could be used with other markers, especially PLT and PDW, in prediction of CVD in patients with severe OSAS.

Complete blood count alterations after six months of continuous positive airway pressure treatment in patients with severe obstructive sleep apnea

STUDY OBJECTIVES

The cardiovascular complications caused by obstructive sleep apnea (OSA) decrease after continuous positive airway pressure treatment (CPAP). Mean platelet volume (MPV), platelet distribution width (PDW), and red cell distribution width (RDW) are newly recognized tools for assessing cardiovascular risk.

METHODS

From a selection of patients with symptoms of nocturnal snoring and/or excessive daytime sleepiness, 36 males with an apnea-hypopnea index (AHI) > 30/h and 22 age-matched normal male controls with AHI < 5/h were included. Patients with OSA underwent another night of CPAP titration, and 11 patients were excluded at the 6-month evaluation due to poor compliance with the home CPAP therapy. Complete blood count parameters of compliant patients and the control group were evaluated.

RESULTS

Compared to controls, MPV values were significantly higher (p = 0.025) in OSA patients, but no significant differences in PDW or RDW were found (p > 0.05). Six months of CPAP therapy resulted in significantly lower MPV values but increased values of PDW and RDW in patients with severe OSA (p = 0.001, p = 0.007, p = 0.001, respectively).

CONCLUSION

Our data suggest that complete blood count parameters in OSA patients such as MPV, PDW and RDW change significantly after CPAP therapy.

[Correlation between urinary catecholamines dosage and apnea-hypopnea index in a hypertension population: pilot study]

AIMS

Sleep disorders like obstructive sleep apnea in adults are associated with increased sympathetic activity, which induced high blood pressure and could be associated with resistant hypertension. Some studies have demonstrated that high urinary catecholamine levels in obstructive sleep apnea patients may be decreased with continuous positive airway pressure therapy. However, very few studies have demonstrated a correlation between apnea-hypopnea index and urinary catecholamine levels in hypertension patients.

METHODS

In this pilot study, 20 hypertensive patients referred for hypertension work-up including night-time polygraphy and 24h urinary catecholamine dosage were included.

RESULTS

Mean age was 51±11 years (30-76), 68% were males. Diagnosis of obstructive sleep apnea was confirmed in 13 patients at the end of the work-up. Mean apnea-hypopnea index was 14±9 (2-32). The only urinary catecholamine parameter significantly increased in patients with obstructive sleep apnea was 24h urinary normetanephrine (1931±1285 vs 869±293nmol/24h; P<0.05). However, this difference was not significant when this parameter was adjusted to 24h urinary creatinine. We observed a significant positive correlation between AHI and 24h urinary normetanephine (r=0.486; P=0.035).

CONCLUSION

This pilot study confirms an isolated elevation of 24h urinary normetanephrine in hypertensive patients with obstructive sleep apnea and shows a significant correlation between sleep disorders expressed by apnea-hypopnea index and urinary catecholamines excretion.

Etiopathogenetic mechanisms of pulmonary hypertension in sleep-related breathing disorders

Obstructive sleep apnea syndrome is a common disorder with significant health consequences and is on the rise in consonance with the obesity pandemic. In view of the association between sleep-disordered breathing and pulmonary hypertension as depicted by multiple studies, current clinical practice guidelines categorize obstructive sleep apnea as a risk factor for pulmonary hypertension and recommend an assessment for sleep disordered breathing in evaluating patients with pulmonary hypertension. The dysregulatory mechanisms associated with hypoxemic episodes observed in sleep related breathing disorders contribute to the onset of pulmonary hypertension and identification of these potentially treatable factors might help in the reduction of overall cardiovascular mortality.

Sympathetic and catecholaminergic alterations in sleep apnea with particular emphasis on children

Sleep is involved in the regulation of major organ functions in the human body, and disruption of sleep potentially can elicit organ dysfunction. Obstructive sleep apnea (OSA) is the most prevalent sleep disorder of breathing in adults and children, and its manifestations reflect the interactions between intermittent hypoxia, intermittent hypercapnia, increased intra-thoracic pressure swings, and sleep fragmentation, as elicited by the episodic changes in upper airway resistance during sleep. The sympathetic nervous system is an important modulator of the cardiovascular, immune, endocrine and metabolic systems, and alterations in autonomic activity may lead to metabolic imbalance and organ dysfunction. Here we review how OSA and its constitutive components can lead to perturbation of the autonomic nervous system in general, and to altered regulation of catecholamines, both of which then playing an important role in some of the mechanisms underlying OSA-induced morbidities.

Hypertension and catecholamine levels in sleep apnoea

BACKGROUND

Sleep-disordered breathing has been strongly associated with systemic hypertension. Increased sympathetic activity in sleep-disordered breathing may be responsible for this association.

METHOD

In this sleep clinic-based study, 82 newly diagnosed patients of sleep-disordered breathing were evaluated for hypertension, and their plasma and urinary levels of catecholamines were measured. Catecholamine levels were then compared separately with the severity of sleep apnoea and blood pressure (BP).

RESULTS

The prevalence of hypertension in the study population was 46.3%. The BP showed a strong and statistically significant correlation with apnoea-hypopnoea index (diastolic, r = 0.65, P < 0.001 and systolic, r = 0.60, P < 0.001) which was maintained even after the results were analysed separately for obese and non-obese subjects. Both plasma and urinary levels of catecholamines were greater in patients with severe sleep apnoea (compared to nonsevere cases) and in those with hypertension compared to normotensives. However, statistical significance was achieved only for urine catecholamines and not for plasma catechol-amines in both the cases.

CONCLUSION

Hypertension is highly prevalent among Indian subjects with obstructive sleep apnoea. Catecholamine levels are significantly higher in hypertensive than in normotensive apnoeics and are also directly related to the severity of obstructive sleep apnoea. Twenty-four hour urinary catecholamine levels are more valid measures of sympathetic activity than spot plasma samples.

Xanthine oxidase inhibition attenuates endothelial dysfunction caused by chronic intermittent hypoxia in rats

BACKGROUND

Xanthine oxidase is a major source of superoxide in the vascular endothelium. Previous work in humans demonstrated improved conduit artery function following xanthine oxidase inhibition in patients with obstructive sleep apnea.

OBJECTIVES

To determine whether impairments in endothelium-dependent vasodilation produced by exposure to chronic intermittent hypoxia are prevented by in vivo treatment with allopurinol, a xanthine oxidase inhibitor.

METHODS

Sprague-Dawley rats received allopurinol (65 mg/kg/day) or vehicle via oral gavage. Half of each group was exposed to intermittent hypoxia (FIO(2) = 0.10 for 1 min, 15×/h, 12 h/day) and the other half to normoxia. After 14 days, gracilis arteries were isolated, cannulated with micropipettes, and perfused and superfused with physiological salt solution. Diameters were measured before and after exposure to acetylcholine (10(-6)M) and nitroprusside (10(-4)M).

RESULTS

In vehicle-treated rats, intermittent hypoxia impaired acetylcholine-induced vasodilation compared to normoxia (+4 ± 4 vs. +21 ± 6 μm, p = 0.01). Allopurinol attenuated this impairment (+26 ± 6 vs. +34 ± 9 μm for intermittent hypoxia and normoxia groups treated with allopurinol, p = 0.55). In contrast, nitroprusside-induced vasodilation was similar in all rats (p = 0.43). Neither allopurinol nor intermittent hypoxia affected vessel morphometry or systemic markers of oxidative stress. Urinary uric acid concentrations were reduced in allopurinol- versus vehicle-treated rats (p = 0.02).

CONCLUSIONS

These data confirm previous findings that exposure to intermittent hypoxia impairs endothelium-dependent vasodilation in skeletal muscle resistance arteries and extend them by demonstrating that this impairment can be prevented with allopurinol. Thus, xanthine oxidase appears to play a key role in mediating intermittent hypoxia-induced vascular dysfunction.

Obstructive sleep apnea and cardiovascular disease

OPINION STATEMENT

Obstructive sleep apnea is a highly prevalent disease that often goes undetected for many years before diagnosis. Although most patients seek treatment to improve symptoms of daytime sleepiness, a growing body of literature suggests that treatment may also modulate cardiovascular risk. This article summarizes the current literature regarding the associations between sleep-disordered breathing and adverse cardiovascular outcomes and reviews the lesser body of data demonstrating the cardiovascular benefits of therapy.

The effects of continuous positive airway pressure therapy on mean platelet volume in patients with obstructive sleep apnea

Previous studies have reported increased platelet activation and aggregation in patients with obstructive sleep apnea (OSA). Continuous positive airway pressure (CPAP) treatment has been shown to decrease platelet activation. We aimed to study the effects of nasal CPAP therapy has on MPV values in patients with severe OSA. Thirty-one patients (21 men; mean age 53.8 ± 9.2 years) with severe OSA (AHI > 30 events/hour) constituted the study group. An age, gender and body mass index (BMI) matched control group was composed 25 subjects (14 men; mean age 49.6 ± 8.5 years) without OSA (AHI < 5 events/hour). We measured MPV values in patients with severe OSA and control subjects and we measured MPV values after 6 months of CPAP therapy in severe OS patients. The median (IQR) MPV values were significantly higher in patients with severe OSA than in control group (8.5 [8.3-9.1] vs. 8.3 [7.5-8.8] fL; p = 0.03). The platelet counts were significantly lower in patients with severe OSA than in control group (217.8 ± 45.9 vs. 265.4 ± 64.0 × 10⁹/L; p = 0.002). The six months of CPAP therapy caused significant reductions in median (IQR) MPV values in patients with severe OSA (8.5 [8.3-9.1] to 7.9 [7.4-8.2] fL; p < 0.001). Six months of CPAP therapy caused significant increase in platelet counts when compared with baseline values (217.8 ± 45.9 to 233.7 ± 60.6 × 10⁹/L; p < 0.001). We have found that the MPV values of patients with severe OSA were significantly higher than those of the control subjects and 6 months CPAP therapy caused significant reductions in the MPV values in patients with severe OSA.

Mean platelet volume is increased in patients with severe obstructive sleep apnea

Increased platelet activation and aggregation which are closely related to cardiovascular complications have been reported in patients with obstructive sleep apnea (OSA). The aim of this study was to assess the mean platelet volume (MPV), an indicator of platelet activation in patients with OSA. The 95 subjects referred for evaluation of OSA underwent overnight polysomnography. Blood samples were taken for MPV determination. According to the apnea-hypopnea index (AHI), subjects were divided into three groups; group 1: control subjects without OSA (AHI < 5, n = 24), group 2: patients with mild to moderate OSA (AHI: 5-30, n = 42), and group 3: severe OSA (AHI > 30, n = 29). Body mass index (BMI) of patients with severe OSA was significantly higher than control subjects (31.5 ± 4.0 vs. 28.2 ± 5.0; p = 0.02). The MPV was significantly higher in patients with severe OSA than in the control group (8.9 ± 1.0 vs. 8.2 ± 0.7 fl; p = 0.01). Correlation analysis within 71 patients with OSA indicated that MPV was correlated with AHI (p < 0.001, r = 0.44) and DI (p = 0.001, r = 0.37). In multivariate regression analysis, when MPV was taken as independent with other study variables which are potential confounders such as age, gender and BMI, MPV was independently correlated with both AHI (β = 0.44, p < 0.001) and DI (β = 0.38, p < 0.001). We have shown that MPV was significantly higher in patients with severe OSA when compared with control subjects and MPV was correlated with AHI and DI.

Transcriptional responses to intermittent hypoxia

Recurrent apneas are characterized by transient repetitive cessations of breathing (two breaths duration or longer) resulting in periodic decreases in arterial blood PO2 or chronic intermittent hypoxia (IH). Patients with recurrent apneas and experimental animals exposed to chronic IH exhibit cardio-respiratory morbidities. The purpose of this article is to highlight the current information on the transcriptional mechanisms associated with chronic IH. Studies on rodents and cell cultures have shown that IH activates a variety of transcription factors including the hypoxia-inducible factor-1 (HIF-1), c-fos (immediate early gene), nuclear factor of activated T-cells (NFAT), and nuclear factor kB (NF-kB). The signaling pathways associated with transcriptional activation associated with IH differ from continuous hypoxia (CH). Compared to same duration and intensity of CH, IH is more potent in activating HIF-1 and c-fos and also results in long-lasting accumulation of HIF-1alpha and c-fos mRNA, a phenomenon that was not seen with CH. IH-evoked transcriptional activation by HIF-1, c-fos as well as the resulting activator protein-1 (AP-1) requires reactive oxygen species (ROS)-mediated signaling and involves complex feed forward interactions between HIF-1 and ROS. Chronic IH-evoked cardio-respiratory responses are absent in Hif-1alpha+/- mice, and hypertension elicited by chronic IH is absent in mice lacking NFAT3c. These studies indicate that cardiorespiratory responses to chronic IH depend on complex interactions between various transcription factors resulting in alterations in several down stream genes and their protein products.

Obstructive sleep apnea and erectile dysfunction: still a neglected risk factor?

INTRODUCTION

Erectile dysfunction (ED) is a well-known entity with determined risk factors, which generally has a negative impact on quality of life. Obstructive sleep-disordered breathing (SDB), often referred to as obstructive sleep apnea, stands among the possible risk factors for ED.

DISCUSSION

Literature review suggests that SDB induces a spectrum of abnormalities in neural, hormonal, and vascular regulation that may contribute to the development of ED. While more studies are required to imply SDB as a risk factor for ED, several case series and expert opinion have contributed evidence for a causal relationship.

CONCLUSION

In clinical practice, men presenting with symptoms of sexual dysfunction often have concomitant sleep disorders requiring treatment. There is now evidence to suggest that treating SDB may be an effective treatment for ED. It is the authors' opinion that patients with erectile dysfunction would benefit from a sleep evaluation.

Comparison of obstructive sleep apnea patients with and without leg edema

BACKGROUND

To determine the proportion of patients with obstructive sleep apnea (OSA) who have leg edema, and to identify differences between edematous and non-edematous OSA patients.

METHODS

Retrospective, cross-sectional study of 378 patients with OSA (apnea/hypopnea index [AHI] >or=15) who had neither heart failure nor chronic lung disease.

RESULTS

Thirty-five percent (133/378) of the subjects with OSA had bilateral leg edema. Eighty-one percent (108/133) of the edematous subjects had mild pitting that was 1+. Compared to the non-edematous OSA subjects, the edematous subjects were older (age=51+/-13 versus 45+/-13 years, p=0.001), more obese (body mass index=39+/-9 versus 33+/-8kg/m(2), p=0.001), had more severe OSA (AHI=46+/-71 versus 27+/-29, p=0.004), spent a greater proportion of sleep time with an oxygen saturation <90% (20+/-26 versus 11+/-18%, p=0.001), and were more likely to have diabetes mellitus (11% versus 3%, p=0.001) and hypertension (32% versus 10%, p=0.001). Age, obesity, hypertension and diabetes mellitus correlated significantly with edema status. After adjusting for these confounding variables, the AHI means remained different between the edema and non-edema groups (41+/-5 versus 28+/-3, p=0.04).

CONCLUSIONS

Approximately one-third of OSA patients have edema. Edematous OSA patients are older, more obese, more likely to have diabetes mellitus and hypertension, and have more severe OSA than OSA patients who lack edema.

Erectile dysfunction and sleep related disorders

PURPOSE

There are reported links between erectile dysfunction and sleep disorders. We reviewed the physiology of penile erection during sleep and the possible links between the pathophysiology of erectile dysfunction and the most commonly diagnosed sleep disorders.

MATERIALS AND METHODS

A MEDLINE search using the identifiers erectile dysfunction, sleep, sleep disorders, sleep apnea, insomnia and narcolepsy was performed to identify the current literature pertaining to erectile dysfunction and sleep disorders. The peer reviewed literature and relevant surveys from 1985 to 2006 were subsequently reviewed.

RESULTS

An association between erectile dysfunction and sleep disorders appears to exist in survey studies relying on self-report and in small case series. Hormonal, neural and endothelial mechanisms have been implicated in linking sleep disorders with erectile dysfunction. Treatment of sleep disorders, specifically sleep apnea with continuous positive airway pressure, has been shown to improve patient erectile function.

CONCLUSIONS

Clinicians should consider concomitant sleep disorders when evaluating patients with erectile dysfunction, especially in those refractory to routine therapy. Further studies are necessary to clearly define the causative link between sleep disorders and erectile dysfunction.

Cellular mechanisms associated with intermittent hypoxia

Hypoxia, i.e. decreased availability of oxygen occurs under many different circumstances and can be either continuous or intermittent. Continuous hypoxia such as that experienced during periods of high altitude leads to physiological adaptations, whereas chronic IH (intermittent hypoxia) associated with sleep-disordered breathing manifested as recurrent apneas leads to morbidity. The purpose of the present chapter is to highlight recent findings on cellular responses to IH. Studies on cell culture models of IH revealed that for a given duration and intensity, IH is more potent than continuous hypoxia in evoking transcriptional activation. IH activates HIF-1 (hypoxia-inducible factor-1), the immediate early gene c-fos, activator protein-1, nuclear factor kappaB and cAMP-response-element-binding protein. Physiological studies showed that HIF-1 plays an important role in chronic IH-induced autonomic abnormalities in mice. IH affects expression of proteins associated with neuronal survival and apoptosis, as well as post-translational modifications of proteins resulting in increased biological activity. Comparisons between continuous hypoxia and IH revealed notable differences in the kinetics of protein kinase activation, type of protein kinase being activated and the downstream targets of protein kinases. IH increases ROS (reactive oxygen species) generation both in cell culture and in intact animals, and ROS-mediated signalling mechanisms contribute to cellular and systemic responses to IH. Future studies utilizing genomic and proteomic approaches may provide important clues to the mechanisms by which IH leads to morbidity as opposed to continuous hypoxia-induced adaptations. Cellular mechanisms associated with IH (other than recurrent apneas) such as repetitive, brief ascents to altitude, however, remain to be studied.

Cardiovascular manifestations seen in obstructive sleep apnea

Patients with obstructive sleep apnea (OSA) have an increased prevalence of systemic and pulmonary hypertension, left ventricular (LV) hypertrophy, LV systolic and diastolic dysfunction, and congestive heart failure, increased platelet aggregability, and increased susceptibility to thrombotic and embolic cardiac and cerebrovascular events. Patients with OSA have an increased prevalence of coronary artery disease, myocardial infarction, nocturnal angina, and myocardial ischemia, arrhythmias, and sudden cardiac death. Patients with OSA also have an increased prevalence of stroke. Treatment of OSA with continuous positive airway pressure improves cardiac efficiency in patients with heart failure, causes a reduction in the frequency of nocturnal ischemic ST-segment depression, relieves nocturnal angina, and causes a reduction in the occurrence of new cardiovascular events and an increase in the time to such events.

Chronic intermittent hypoxia alters hypothalamic transcription of genes involved in metabolic regulation

Epidemiological studies show that the obstructive sleep apnea syndrome (OSAS) is strongly associated with obesity, hypertension and diabetes, the three conditions characteristic of the metabolic syndrome. Since metabolic disorders usually involve altered homeostatic mechanisms both centrally and peripherally, it is likely that so it is in OSAS, but the underlying mechanisms remain largely unknown. We used an established rodent model to test whether chronic intermittent hypoxia (CIH) similar to that experienced by OSAS patients leads to distinct and relevant for metabolic regulation transcriptional changes in the posterior hypothalamus. Using quantitative reverse transcription-polymerase chain reaction, we found that rats exposed to CIH for 35 days (n=9) had twice higher levels of the adrenergic alpha2A receptor mRNA than the rats simultaneously submitted to a matching sham treatment (n=9). The mRNA levels of three members of the family of signal transducers and activators of transcription, STAT1, STAT3 and STAT5b, were also increased 2-4 times. The increases occurred only in the perifornical region, whereas no changes were detected in the ventromedial region comprising the ventromedial and arcuate nuclei or the dorsomedial region comprising the dorsomedial and paraventricular nuclei. These results show that, at least at the transcriptional level, CIH exerts a distinct and regionally selective central effect on the expression of selected mRNAs involved in metabolic regulation through adrenergic, leptinergic and inflammatory pathways.

Modifying effects of the R389G beta1-adrenoceptor polymorphism on resting heart rate and blood pressure in patients with obstructive sleep apnoea

OSA (obstructive sleep apnoea) stimulates sympathetic nervous activity and elevates resting HR (heart rate) and BP (blood pressure). In the present study in a cohort of 309 untreated OSA patients, the resting HR and BP during the daytime were correlated with AHI (apnoea/hypopnea index) and compared with patients with R389R (n = 162), R389G (n = 125) and G389G (n = 22) genotypes of the beta1-adrenoreceptor R389G polymorphism. We analysed the impact of the genotype on the decline of HR and BP in a subgroup of 148 patients (R389R, n = 86; R389G, n = 54; G389G, n = 8) during a 6-month follow-up period under CPAP (continuous positive airway pressure) therapy during which cardiovascular medication remained unchanged. In untreated OSA patients, we found an independent relationship between AHI and resting HR (beta = 0.096, P < 0.001), systolic BP (beta = 0.09, P = 0.021) and diastolic BP (beta = 0.059, P = 0.016). The resting HR/BP, however, did not differ among carriers with the R389R, R389G and G389G genotypes. CPAP therapy significantly reduced HR [-2.5 (-1.1 to -4.0) beats/min; values are mean difference (95% confidence intervals)] and diastolic BP [-3.2 (-1.5 to -5.0) mmHg]. The decline in HR was more significantly pronounced in the R389R group compared with the Gly(389) carriers [-4.1 (-2.3 to -5.9) beats/min (P < 0.001) compared with -0.2 (2.1 to -2.6) beats/min (P = 0.854) respectively; Student's t test between groups, P = 0.008]. Diastolic BP was decreased significantly (P < 0.001) only in Gly389 carriers (R389G or G389G) compared with R389R carriers [-5.0 (-2.3 to -7.6) mmHg compared with -2.0 (0.4 to -4.3) mmHg respectively]. ANOVA revealed a significant difference (P = 0.023) in HR reduction between the three genotypes [-4.1 (+/-8.4) beats/min for R389R, -0.5 (+/-9.3) beats/min for R389G and +1.9 (+/-7.2) beats/min for G389G]. In conclusion, although the R389G polymorphism of the beta1-adrenoceptor gene did not influence resting HR or BP in untreated OSA patients, it may modify the beneficial effects of CPAP therapy on these parameters.

Effects of nasal continuous positive airway pressure and oxygen supplementation on norepinephrine kinetics and cardiovascular responses in obstructive sleep apnea

Obstructive sleep apnea (OSA) is characterized by noradrenergic activation. Nasal continuous positive airway pressure (CPAP) is the treatment of choice and has been shown to effectively reduce elevated norepinephrine (NE) levels. This study examined whether the reduction in NE after CPAP is due to an increase in NE clearance and/or a decrease of NE release rate. Fifty CPAP-naive OSA patients with an apnea-hypopnea index >15 were studied. NE clearance and release rates, circulating NE levels, urinary NE excretion, and blood pressure and heart rate were determined before and after 14 days of CPAP, placebo CPAP (CPAP administered at ineffective pressure), or oxygen supplementation. CPAP led to a significant increase in NE clearance ( P ≤ 0.01), as well as decreases in plasma NE levels ( P ≤ 0.018) and daytime ( P < 0.001) and nighttime ( P < 0.05) NE excretion. NE release rate was unchanged with treatment. Systolic ( P ≤ 0.013) and diastolic ( P ≤ 0.026) blood pressure and heart rate ( P ≤ 0.014) were decreased in response to CPAP but not in response to oxygen or placebo CPAP treatment. Posttreatment systolic blood pressure was best predicted by pretreatment systolic blood pressure and posttreatment NE clearance and release rate ( P < 0.01). The findings indicate that one of the mechanisms through which CPAP reduces NE levels is through an increase in the clearance of NE from the circulation.

Role of oxidative stress in intermittent hypoxia-induced immediate early gene activation in rat PC12 cells

Intermittent hypoxia (IH) occurs in many pathophysiological conditions. The molecular mechanisms associated with IH, however, have received little attention. Previous studies have reported that the c-fos gene via formation of activator protein-1 (AP-1) transcription factor contributes to adaptive responses to continuous hypoxia. In the present study, using a cell culture model we examined whether IH activates c-fos and AP-1 and if so, by what mechanisms. Experiments were performed on rat phaeochromocytoma cells exposed to 21% O(2) (normoxia) or 60 and 120 cycles of IH, each cycle consisting 15 s of hypoxia followed by 4 min of normoxia. IH resulted in a significant elevation of c-fos mRNA as well as transcriptional activation. IH was more potent and induced a longer lasting activation of c-fos than comparable cumulative duration of continuous hypoxia. IH increased AP-1 activity and tyrosine hydroxylase (TH) mRNA, an AP-1-regulated downstream gene, and these effects were prevented by antisense c-fos. Superoxide dismutase mimetic, a potent scavenger of superoxide anions, prevented IH-induced c-fos, AP-1 and TH activations. IH increased superoxide anion levels in mitochondria as evidenced by decreased aconitase enzyme activity and increased levels of hydrogen peroxide, a stable dismutated product of superoxide anions. Complex I of the mitochondrial electron transport chain was markedly inhibited in IH exposed cells. Pharmacological inhibitors of complex I mimicked the effects of IH during normoxia and occluded the effects of IH on c-fos activation, suggesting the involvement of the mitochondrial electron transport chain in the generation of superoxide anions during IH. These results suggest IH-induced c-fos-mediated transcriptional activation involves oxidative stress.

Disordered sleep, nocturnal cytokines, and immunity: interactions between alcohol dependence and African-American ethnicity

Sleep disturbance is one of the most prominent complaints of alcohol-dependent patients. In view of recent evidence that the immune system is integrated with other homeostatic processes ultimately regulated by the brain, the influence of sleep on host defense mechanisms and the expression of proinflammatory and T helper cell cytokines deserves attention in alcohol dependence. Although not all immune alterations found in alcohol-dependent persons are related to disordered sleep, it is exceedingly important to know whether sleep influences immunity in alcoholism because of the recognized impact of disordered sleep on infectious disease risk. Conversely, feedback systems are also operating between the brain and the immune system, and abnormalities in the expression of cytokines might contribute to sleep disturbances in alcohol-dependent persons. In this review, we identify the immune alterations found in association with alcohol dependence and discuss the implications of these findings for infectious disease risk, with particular attention to the interaction between African-American ethnicity and alcoholism in contributing to this risk. We provide evidence that sleep disruption occurs in association with alcohol dependence and that African-American alcohol-dependent persons show greater abnormalities in sleep and sleep regulatory processes than shown by Euro-American alcohol-dependent persons. The relations among alcoholism, sleep, and immunity are discussed, with an emphasis on understanding how the cytokine network is altered during sleep in the African-American alcohol-dependent populations. The potential is to use cytokine agonists or antagonists to determine whether physiologic changes in cytokines have a role in the homeostatic regulation of sleep in human beings, which has tremendous implications for the development of novel treatments of alcohol-related sleep disorders.

Clinical significance of nocturnal oximeter monitoring for detection of sleep apnea syndrome in the elderly

OBJECTIVES

The sensitivity and specificity of overnight monitoring of arterial oxygen saturation (SaO(2)) using an oximeter were evaluated in elderly subjects who are being investigated for possible sleep apnea syndrome (SAS).

METHODS

Seventy-five consecutive elderly subjects with habitual snoring (47 men, 28 women; mean (+/-SE) age 75.5+/-0.9 years (range 65-94 years)) were studied. The SaO(2) was measured with an oximeter and a chart recorder during the night immediately before detailed polysomnographic studies. The SaO(2) recordings were classified by two observers as positive or negative using a number of significant oxyhemoglobin desaturation (SDS) of more than 2, 4, and 6%. The sensitivity of the oximeter alone for the recognition of the SAS was calculated as the number of true positive SaO(2) records divided by the total number of positive definitive (polysomnographic) records. The specificity was defined as the number of true negative SaO(2) records divided by the total number of negative definitive records.

RESULTS

Of the 75 subjects, 24 had moderate SAS (apnea index (AI)>15) and 55 had mild to moderate SAS (AI>5). The sensitivity and specificity of the dosimeter as a screening test were determined with the two diagnostic thresholds of the AI. For AI exceeding 5 or 15, the respective sensitivity by using the criterion of SDS of more than 4% was 85.5 or 91.7%, with corresponding specificity of 85.0 or 92.2%.

CONCLUSIONS

The nocturnal oximeter monitoring allows recognition of elderly subjects with a mild to moderate SAS, and 4% desaturation of SaO(2) is a candidate index to detect a significant number of apneas in elderly SAS patients with an oximeter.

Facilitation of dopamine and acetylcholine release by intermittent hypoxia in PC12 cells: involvement of calcium and reactive oxygen species

We have investigated the effects of preconditioning pheochromocytoma (PC12) cells with intermittent hypoxia (IH) on transmitter release during acute hypoxia. Cell cultures were exposed to either alternating cycles of hypoxia (1% O(2) + 5% CO(2); 30 s/cycle) and normoxia (21% O(2) + 5% CO(2); 3 min/cycle) for 15 or 60 cycles or normoxia alone (control) for similar durations. Control and IH cells were challenged with either hyperoxia (basal release) or acute hypoxia (Po(2) of approximately 35 Torr) for 5 min, and the amounts of dopamine (DA) and acetylcholine (ACh) released in the medium were determined by HPLC combined with electrochemical detection. Hypoxia augmented DA (approximately 80%) but not ACh release in naive cells, whereas, in IH-conditioned cells, it further enhanced DA release (ranging from 120 to approximately 145%) and facilitated ACh release (approximately 30%). Hypoxia-evoked augmentation of transmitter release was not seen in cells conditioned with sustained hypoxia. IH-induced increase in DA but not IH-induced ACh release during hypoxia was partially inhibited by cadmium chloride (100 microM), a voltage-gated Ca(2+) channel blocker. By contrast, 2-aminoethoxydiphenylborate (75 microM), a blocker of inositol 1,4,5-trisphosphate (IP(3)) receptors, and N-acetyl-L-cysteine (300 microM), a potent scavenger of reactive oxygen species, either attenuated or abolished IH-evoked augmentation of transmitter release during hypoxia. Together, the above results demonstrate that IH conditioning increases hypoxia-evoked neurotransmitter release from PC12 cells via mechanisms involving mobilization of Ca(2+) from intracellular stores through activation of IP(3) receptors. Our findings also suggest that oxidative stress plays a central role in IH-induced augmentation of transmitter release from PC12 cells during acute hypoxia.

Vascular reactivity to norepinephrine and acetylcholine after chronic intermittent hypoxia in mice

This study assessed the early vascular reactivity changes in mice after exposure to 14 days intermittent hypoxia (IH) with active or inactive sympathetic nervous system (SNS). Hindquarters of mice exposed to 14 days of IH, sham exposed mice or unhandled mice were perfused at constant flow with Krebs-Albumin (5%). Changes in perfusion pressure were assessed after injection of several doses of norepinephrine in anaesthetized mice (active SNS) or in euthanized mice (inactive SNS). Response to several doses of acetylcholine was recorded after precontraction of hindquarter vascular bed by methoxamine in euthanized mice. Vasoconstrictor response was increased after IH for high dose of NE (50 microg) in euthanized mice and for all doses of NE (2-10-50 microg) in anaesthetized mice, but no change in vasodilatation was observed. These findings suggest that 14 days of IH altered vascular reactivity of mice hindquarter in an early pattern. Vasoconstriction was enhanced, particularly with active SNS, while there was no dysfunction of endothelium-relaxation.

Insulin resistance and obstructive sleep apnea: is increased sympathetic stimulation the link?

The science of sleep is in early stages of development, and the biochemical consequences of obstructive sleep apnea (OSA) are slowly being identified. Only recently have investigators begun to identify the commonalities and interaction between OSA and insulin resistance, the underlying pathology of type 2 diabetes. Obesity and increasing age play important parts in the natural history of both conditions, which frequently coexist. The purpose of this article is, first, to examine the extent and strength of studies that have investigated the association between OSA and increased insulin resistance or type 2 diabetes and, second, to propose a model that explains the association and cyclical interaction between OSA, obesity, and insulin resistance.

Snoring as a cause of nocturia in men with lower urinary tract symptoms

OBJECTIVES

Snoring increases with increasing age and body mass, and repeated periods of hypoxia cause nocturnal polyuria. Accordingly, we examined the occurrence of snoring problems in patients scheduled for transurethral prostatic resection.

METHODS

Of 171 men scheduled for TUR-P, 41 were excluded due to cardiac disease, diabetes, or prostatic malignancy. Of the remaining 130 patients, 12% were troubled by snoring that disturbed their sleep. The severity of their snoring was evaluated by questionnaires, micturition charts, and determination of nocturnal capillary oxygen saturation (SaO(2)) and pulse rate. Plasma levels of cortisol, arginine vasopressin (AVP), and atrial natriuretic peptide (ANP) were measured in the morning and at 2 p.m. Fifteen non-snoring patients also scheduled for TUR-P served as controls.

RESULTS

Compared to controls, the snoring patients had a significantly higher body mass index (BMI), voided more frequently, and produced more urine at night. They also had a significantly larger number of hypoxic episodes at night, which, along with low SaO(2) levels, correlated with the nocturnal diuresis. Snorers did not differ significantly from controls in regard to excretion of cortisol and AVP, but they did have higher plasma levels of ANP.

CONCLUSIONS

We recommend that elderly obese men with urgency at night be questioned about snoring, and that micturition frequency and volume charts be completed before deciding to operate.

Disordered sleep, nocturnal cytokines, and immunity in alcoholics

OBJECTIVE

Alcoholics who are at risk for infectious disease show profound disturbances of sleep along with decrements of cellular immunity. This study examined the relationships between sleep, nocturnal expression of immunoregulatory cytokines, and natural killer (NK) cell activity in alcoholic patients as compared with control subjects.

METHODS

Alcoholic patients (N = 24) and comparison control subjects (N = 23) underwent all-night polysomnography and serial blood sampling at 23:00, 03:00, and 06:30 hours. Stimulated expression of T(H)1 (interferon gamma, IFN-gamma), anti-inflammatory/T(H)2 (interleukin 10, IL-10), and proinflammatory cytokines (IL-6) was measured along with NK cell activity across the night.

RESULTS

Alcoholic patients showed lower levels of IL-6 production, suppression of the IL-6/IL-10 ratio, and a reduction of NK cell activity, coupled with losses of delta sleep and increases of rapid eye movement sleep, as compared with control subjects. In addition, alcoholics showed a persistent low ratio of IFN-gamma/IL-10 and reduced levels of NK cell activity, whereas controls had increases of these two immune measures across the night. IL-6 also differentially changed in the two groups; alcoholics showed increases and controls had decreases of IL-6 from 03:00 hours to 06:30 hours. At 06:30 hours, rapid eye movement sleep predicted increases of IL-6 and decreases of NK cell activity independent of the relative contribution of age and chronic alcohol consumption. At 23:00 hours before sleep onset, levels of IL-10 predicted subsequent amounts of delta sleep.

CONCLUSIONS

These data further implicate sleep in the regulation of immune function and suggest that disordered sleep contributes to immune alterations in patients with chronic alcoholism. Moreover, the association between awake levels of the anti-inflammatory/T(H)2 cytokine IL-10 and subsequent amounts of delta sleep support the notion of a bidirectional interplay between cytokines and sleep in humans.